C++实现编码转换的示例代码

    代码地址

    https://github.com/gongluck/Code-snippet/tree/master/cpp/code%20conversion

    需求

    编码转换在实际开发中经常遇到,通常是ANSI、Unicode和Utf-8之间相互转换。实现也有很多种,有查表法、使用C++11、使用boost、使用系统API。C++11和boost几乎可以实现一套代码,在linux和windows都能使用,但实际会有很多坑,相当于代码几乎不改,但是要改一下系统环境。所以有一种实现就是判断系统的版本,然后选择不同的系统api进行编码转换。

    实现

    目前只实现Windows下的编码转换,以后需要在linux下使用编码转换再做补充。windows下的编码转换基本围绕unicode做处理。例如ANSI->UTF-8,就是先将ANSI->unicode,再将unicode->UTF-8。

    
    // convert.h
    /*
     * @Author: gongluck 
     * @Date: 2020-03-23 16:06:23 
     * @Last Modified by: gongluck
     * @Last Modified time: 2020-03-23 16:09:30
     */
    
    // Character encoding conversion
    
    #pragma once
    
    #include <string>
    
    namespace gconvert
    {
    // ANSI->Unicode
    int ansi2uni(const std::string& ansi, std::wstring& uni);
    
    // Unicode->ANSI
    int uni2ansi(const std::wstring& uni, std::string& ansi);
    
    // UTF8->Unicode
    int utf82uni(const std::string& utf8, std::wstring& uni);
    
    // Unicode->UTF8
    int uni2utf8(const std::wstring& uni, std::string& utf8);
    
    // ANSI->UTF8
    int ansi2utf8(const std::string& ansi, std::string& utf8);
    
    // UTF8->ANSI
    int utf82ansi(const std::string& utf8, std::string& ansi);
    } // namespace gconvert
    
    //convert.cpp
    /*
     * @Author: gongluck 
     * @Date: 2020-03-23 16:13:01 
     * @Last Modified by: gongluck
     * @Last Modified time: 2020-03-23 16:34:50
     */
    
    #include "convert.h"
    
    #include <iostream>
    
    #ifdef _WIN32
    #include <windows.h>
    #endif
    
    namespace gconvert
    {
    #ifdef _WIN32
     static int multi2uni(const std::string& multi, std::wstring& uni, UINT code)
     {
      auto len = MultiByteToWideChar(code, 0, multi.c_str(), -1, nullptr, 0);
      if (len <= 0)
      {
       std::cerr << __FILE__ << " : " << __LINE__ << " : " << GetLastError() << std::endl;
       return -1;
      }
      WCHAR* buf = new WCHAR[len];
      if (buf == nullptr)
      {
       std::cerr << __FILE__ << " : " << __LINE__ << " : " << "can not new buf, size : " << len << std::endl;
       return -2;
      }
      len = MultiByteToWideChar(code, 0, multi.c_str(), -1, buf, len);
      uni.assign(buf);
      delete[]buf;
      buf = nullptr;
      return len;
     }
    
     static int uni2multi(const std::wstring& uni, std::string& multi, UINT code)
     {
      auto len = WideCharToMultiByte(code, 0, uni.c_str(), -1, nullptr, 0, nullptr, nullptr);
      if (len <= 0)
      {
       std::cerr << __FILE__ << " : " << __LINE__ << " : " << GetLastError() << std::endl;
       return -1;
      }
      CHAR* buf = new CHAR[len];
      if (buf == nullptr)
      {
       std::cerr << __FILE__ << " : " << __LINE__ << " : " << "can not new buf, size : " << len << std::endl;
       return -2;
      }
      len = WideCharToMultiByte(code, 0, uni.c_str(), -1, buf, len, nullptr, nullptr);
      multi.assign(buf);
      delete[]buf;
      buf = nullptr;
      return len;
     }
    #endif
    
    // ANSI->Unicode
    int ansi2uni(const std::string& ansi, std::wstring& uni)
    {
    #ifdef _WIN32
     return multi2uni(ansi, uni, CP_ACP);
    #endif
     return 0;
    }
    
    // Unicode->ANSI
    int uni2ansi(const std::wstring &uni, std::string &ansi)
    {
    #ifdef _WIN32
     return uni2multi(uni, ansi, CP_ACP);
    #endif
     return 0;
    }
    
    // UTF8->Unicode
    int utf82uni(const std::string& utf8, std::wstring& uni)
    {
    #ifdef _WIN32
     return multi2uni(utf8, uni, CP_UTF8);
    #endif
     return 0;
    }
    
    // Unicode->UTF8
    int uni2utf8(const std::wstring& uni, std::string& utf8)
    {
    #ifdef _WIN32
     return uni2multi(uni, utf8, CP_UTF8);
    #endif
     return 0;
    }
    
    // ANSI->UTF8
    int ansi2utf8(const std::string &ansi, std::string &utf8)
    {
     std::wstring uni;
     auto len = ansi2uni(ansi, uni);
     if (len <= 0)
     {
      return -3;
     }
     return uni2utf8(uni, utf8);
    }
    
    // UTF8->ANSI
    int utf82ansi(const std::string &utf8, std::string &ansi)
    {
     std::wstring uni;
     auto len = utf82uni(utf8, uni);
     if (len <= 0)
     {
      return -3;
     }
     return uni2ansi(uni, ansi);
    }
    } // namespace gconvert
    
    //testcode
    #include <iostream>
    
    #include "../code conversion/convert.h"
    
    int main()
    {
     std::string ansi = "你好,世界!";
     std::wstring uni;
     std::string utf8;
     ret = gconvert::ansi2uni(ansi, uni);
     ret = gconvert::ansi2utf8(ansi, utf8);
     ret = gconvert::uni2ansi(uni, ansi);
     ret = gconvert::uni2utf8(uni, utf8);
     ret = gconvert::utf82ansi(utf8, ansi);
     ret = gconvert::utf82uni(utf8, uni);
     return 0;
    }

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